The present invention pertains to highly reliable data transmission and more particularly to flexible, minimal circuitry for duplex multiple port data transmission.
Data processing and transmission systems must communicate with other remotely located data processing systems. These data processing systems may communicate via a variety of data transmission types. These types include RS-232 applications (bipolar, 25 pin interfaces) or RS-449 applications (differential, 37 pin interfaces). Traditionally, each such interface circuit is mounted on a separate printed wiring card. As a result, one printed wiring card is required for each interface circuit type. For highly reliable circuit applications, duplication of these printed wiring cards is an expensive scheme which achieves duplex operation. This scheme is wasteful of space and components since one printed wiring card must be used for each copy of the transmission interface circuit.
In addition to the large number of printed wiring cards required to develop a highly reliable multiport data transmission system, such designs are inflexible in that connectors must be changed from one printed wiring card to another and back plane wiring must be added or removed as required. Providing these cabling changes and back plane wiring changes requires a sizable manual effort and such changes are subject to human error.
Accordingly, it is an object of the present invention to provide a highly reliable multiple port serial link controller with a minimum of printed wiring cards or manual intervention required to switch between transmission types.